Paul Knowles' interest in new crops for California agriculture led him to a research career focused mainly on oil seed crops, in particular safflower. Due in large part to his research, safflower was shown to be well-adapted to California and consequently became established as an economically important crop in the state. In the late 1950's and mid 1960's, Knowles traveled over 32,000 miles with his wife and son overland across North Africa, the Middle East, and South Asia gathering germplasm of wild and domesticated safflower species, an effort which produced most of the species now in the USDA world safflower collection.
Together with his students, Knowles worked out the cytotaxonomic relationships among not only all the safflower species but also between these species and their wild relatives. His interest in genetic modification of the fatty acid composition of vegetable oils led him to bring this fundamental knowledge to bear via the development of additional oils in safflower. One of his plant introductions, for example, carried the gene ol, which modifies safflower oil from a high linoleic to a high oleic type. Knowles' cultivar UC1 was the first commercial safflower variety with this important trait.
Over his 35 year tenure at UC Davis, Knowles published 160 papers on flax, soybean, safflower, and cruciferous species. Indeed, in addition to his interests in the breeding, genetics, cytogenetics, and germplasm conservation of safflower, he made important contributions to sunflower improvement and soybean research. He lectured frequently and was strongly committed to the teaching of plant breeding, as evidenced by the important 1967 text Introduction to Plant Breeding that he co-authored with Dr. Fred Briggs. And as chair of the Department of Agronomy and Range Sciences, the "father of California safflower" used his position to spearhead a statewide organization of plant breeders to promote inter-institutional communication and exchange.
The Shields Library Special Collections feature multiple resources on Dr. Knowles' work:
Safflower in California - The Paulden F. Knowles personal history of plant exploration and research on evolution, genetics, and breeding. Edited by Patrick E. McGuire, Ardeshir B. Damania, and Calvin O. Qualset. Agronomy Progress Report No. 313, Dept. of Plant Sciences, University of California, Davis CA USA.